1. Field of the Invention
The present invention relates to the proximity sensing technology, and more particularly to an apparatus with both touch sensing and electrical field sensing functions and an interactive apparatus using the same.
2. Related Art
Recently, due to advances in technology, many control buttons, such as the buttons of an elevator or the buttons of an electronic game console, have been modified from the conventional mechanical spring buttons to the touch sensors. FIG. 1 is a circuit diagram of a conventional touch (capacitive) sensor. Referring to FIG. 1, this circuit comprises a sensing electrode 101, a resistor 102 and a sensing control terminal 103. In this circuit, the sensing electrode 101 is equivalent to a grounded capacitor Cx.
FIG. 2 shows operation waveforms of a conventional capacitive sensor at a coupling node A between the sensing electrode 101 and the resistor 102. Referring to FIGS. 1 and 2, after the sensing control terminal 103 starts to charge the node A to a first rated voltage V20 and keeps the node A in a high impedance state, the sensing electrode 101 starts to discharge through the resistor 102 because the sensing electrode 101 is equivalent to a grounded capacitor Cx. The sensing control terminal 103 continuously detects the voltage of the node A. When the voltage of the node A is discharged to a second rated voltage V21, the sensing control terminal 103 determines whether a finger touches the sensing electrode 101 or not according to a period, during which the node A is discharged from the first rated voltage V20 to the second rated voltage V21, and again charges the node A.
Referring again to FIG. 2, the waveform 201 is the waveform at the node A when the finger does not touch the sensing electrode 101, while the waveform 202 is the waveform at the node A after the finger touches the sensing electrode 101. According to the waveform chart, when the finger touches the sensing electrode 101, the equivalent capacitance of the capacitor Cx of the sensing electrode 101 is increased, so the discharge period T2 of the waveform 202 is longer than the discharge period T1 of the waveform 201. Thus, as long as the sensing control terminal 103 determines that the period, during which the node A is discharged to the second rated voltage V21, is longer than T1, the sensing electrode 101 can be determined as being touched.
Under the condition that the touch sensors are popularized, many plush toys interacts with the human according to the installation of the touch sensor. However, this interaction is only limited to the interaction from the human to the toy. Regarding the toy's self touch sensing, such as that the toy can sense the behavior, such as clapping, belly touching or the like, the existing art needs to add a micro switch, an infrared sensor (IR sensor) or a gravity sensor (G sensor) to the toy. In other words, the additional circuit or element is necessary. If the sensing capability of the touch sensor is to be enhanced, both conditions cannot be properly satisfied because the capacitance difference between the toy's capacitor and the human body is extremely large. Thus, the sensing tends to be induced by the inadvertently touch of the human body, and the problem of the poor self-sensing also occurs.